This disclosure generally relates to systems and methods for determining the location (i.e., position and orientation) of a user or device relative to a coordinate system of a target object. The target object may, for example, be an airplane or a building.
Determining the location of a user or device in the world has applications and benefits too many to list here, but in most situations this is limited to cases in which the user or device is located outdoors (i.e., not inside a structure) where technologies like GPS are available and relatively accurate. When the user or device is indoors (i.e., inside a structure), the problem becomes much more difficult because GPS may no longer provide accurate data, if it provides any data at all. A variety of other technologies (differential GPS, WiFi, RFID, laser) and approaches (triangulation, signal strength, time of flight) have been tried and all have usability issues, such as: the cost and time for instrumenting the environment can both be significant; signals may not be available everywhere; and the position estimates provided can be greatly degraded due to multipath distortion.
Motion capture tracking provides accurate location tracking, but requires the installation of multiple cameras in the environment. MEMS-based inertial measurement units (IMUs) have also been used for position and orientation tracking. IMU-based orientation tracking may work well, but position measurement using an IMU alone is not accurate due to drift issues. Some limited applications that use IMUs mounted to a shoe can give reasonable position data for walking applications—if the user is willing to wear the IMU on a shoe and deal with other idiosyncrasies.
Simultaneous localization and mapping (SLAM) methods use camera or laser-based devices to track features in an environment while moving. These methods can determine the position and orientation of the device relative to the environment, but they have trouble disambiguating objects in environments with repetitive features.
It would be advantageous to provide a system and a method for determining locations which can be used with three-dimensional (3-D) applications (such as 3-D visualization) for discrete or continuous real-time tracking of a device (e.g., a handheld imaging device being used by a person or by an automated system such as a robot) in situations that may contain repetitive features.